1. Technical Field
This invention relates to a transmission and, more particularly, to a mechanical variable reversible transmission eliminating the need for a clutch to change gears between forward, neutral and reverse positions.
2. Prior Art
It has heretofore been proposed to use a belt-pulley type transmission for automobile driving systems. In such driving systems, the transmission is required to have an ability of transmitting the engine rotation in a reverse direction as well as in a forward direction. For the purpose, the transmission is provided with a reverse drive gear mechanism.
For example, U.S. Pat. No. 4,673,377 to Akutagawa discloses a belt-pulley type transmission having a forward-reverse selecting gear mechanism provided between the power clutch and the input member of the belt-pulley mechanism. In the proposed transmission, however, problems have been encountered in that the direction of rotation of the input member of the belt-pulley mechanism is changed between the forward and reverse drive modes. Such change in the direction of rotation of the input member causes a change in the direction of the torque which is being transmitted by the belt so that the life of the belt is shortened to an undesirable extent.
Unfortunately, conventional gear-changing transmissions are expensive, complicated and inefficient in design. The requirement to constantly shift gears also creates “gaps” when accelerating. Thus, the operation of conventional transmissions do not provide smooth acceleration and require the need to manually shift gears between forward, neutral and reverse positions. Another shortcoming of conventional prior art is that they require a significant number of mechanical parts to transfer engine power to usable torque and, therefore, such prior art require more maintenance.